Appendix C-4 | Model 888 ATEX IECEx Tail Gas Analyzer
Period 8 – Track Photo-Span Calibration
This is an intermediate state that is used to determine the next period. The
next period will normally be Period 3 unless a steam blowback has been
triggered. In that event the next period will be Period 9.
Steam Blowback
Analyzers equipped with the steam blowback option will force steam
through the demister to eliminate the build-up of salts. A steam blowback
can be initiated manually or configured to occur after a programmed
number of photo-span calibration cycles. The data valid contact will be
open and the analog outputs held at their last valid value during Periods 9
through 11.
Period 9 – Pre-Steam Flush
Instrument air is flushed through the sample cell during this period. The
analyzer advances to Period 10 once the timer elapses.
Period 10 – Steam Blowback
Steam is directed through the demister and back into the process. Dur-
ing this time the sample cell is isolated to prevent any contamination. The
analyzer will advance to Period 10 once the timer elapses.
Period 11 – Post Steam Flush
The sample system is flushed by instrument air during this period. The
analyzer reverts to Period 5 once the timer elapses.
Special Periods
There are three special periods (12, 13, and 14) used for troubleshooting.
The data valid contact will be open and the analog outputs held at their
last valid value during Periods 12 through 14.
Period 12 – Continuous Flush
The sample system is continuously flushed by instrument air during this
period.
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